Heat is often created as a byproduct of industrial processes where flowing streams of liquids, solids or gasses that contain heat must be exhausted into the environment or removed in some way in an effort to maintain the operating temperatures of the industrial process equipment. Sometimes the industrial process can use heat exchanger devices to capture the heat and recycle it back into the process via other process streams. Other times it is not feasible to capture and recycle this heat because it is either too high in temperature or it may contain insufficient mass flow. This heat is referred to as “waste” heat. Waste heat is typically discharged directly into the environment or indirectly through a cooling medium, such as water.
Waste heat can be utilized by turbine generator systems which employ a well known thermodynamic method known as the Rankine cycle to convert heat into work. Typically, this method is steam-based, wherein the waste heat is used to create steam in a boiler to drive a turbine. The steam-based Rankine cycle is not always practical because it requires heat source streams that are relatively high in temperature (600° F. or higher) or are large in overall heat content. The complexity of boiling water at multiple pressures/temperatures to capture heat at multiple temperature levels as the heat source stream is cooled, is costly in both equipment cost and operating labor. The steam-based Rankine cycle is not a realistic option for streams of small flow rate and/or low temperature.
There exists a need in the art for a system that can efficiently and effectively produce power from not only waste heat but also from a wide range of thermal sources.